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Limit speed and friction coefficient of bearing

Limit speed and friction coefficient of bearing


The speed of the bearing is mainly limited by the temperature rise caused by friction and heat in the bearing. When the speed exceeds a certain limit, the bearing cannot continue to rotate due to burns.The limit speed of the bearing refers to the limit value that does not produce the friction heat that causes burns and can be continuously rotated.


Therefore, the ultimate speed of the bearing depends on the type, size and precision of the bearing and the lubrication mode, the quality and quantity of the lubricant, the material and type of the cage, the load conditions and other factors.The limit speed of all kinds of bearings when they are lubricated by grease and oil (oil bath lubrication) is respectively shown in the bearing size table. The value indicates that the bearings of standard design are under general load conditions (C/P>= 13, Fa/Fr<The limit value of the rotation speed when rotating.In addition, depending on the type and brand, lubricants may be superior to other properties but not suitable for high-speed rotation.

C/P<When the equivalent dynamic load P exceeds about 8% of the basic rated dynamic load C, or the axial load in the composite load exceeds 25% of the radial load, the following formula shall be used to correct the limit speed.Na =f1*f2*n here na: revised limit speed, RPM f1: correction factor f2: correction factor related to load conditions, n: limit speed under general load conditions, RPM (refer to bearing size table) C: basic rated dynamic load, n {KGF} P: equivalent dynamic load, n {KGF} Fr: radial load, n {KGF} Fa:Limit speed of ball bearing with sealing ring (RS type) the limit speed of ball bearing with contact ring (RS type) is limited by the linear speed of the contact surface of the sealing ring. The allowable linear speed depends on the rubber material of the sealing ring.

When the bearing rotates at high speed, especially when the speed is close to or beyond the limit speed recorded in the dimension list, the following matters should be paid attention to:

(1) use precision bearings

(2) analyze the internal clearance of bearing (considering the reduction of internal clearance caused by temperature rise)

(3) analyze the material type of the cage (for high speed rotation, it is suitable to use copper alloy or phenolic resin to cut the cage.There are also synthetic resin shaped retainers for high speed rotation.)

(4) analysis of lubrication method (lubrication is suitable for high speed rotating cycle, spray lubrication, and lubrication oil mist lubrication and oil lubrication methods), the friction coefficient of bearing (reference) compared with sliding bearing, for ease of rolling bearing friction torque can be calculated on bearing inner diameter by type: M = uPd / 2 M here: friction torque, mN. M {KGF. Mm} u: the coefficient of friction, bearing load, N {KGF} d: bearing nominal diameter, mm u friction coefficient by bearing type, bearing load, the influence of the rotational speed, lubrication, etc.

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